array.js

var TILEDMapClass = Class.extend({
    currMapData: null,

    tilesets: [],

    numXTiles: 100,
    numYTiles: 100,

    tileSize: {
        "x": 64,
        "y": 64
    },

    pixelSize: {
        "x": 64,
        "y": 64
    },

    imgLoadCount: 0,

    fullyLoaded: false,

    load: function (map) {
        xhrGet(map, function (data) {
            gMap.parseMapJSON(data.responseText);
        });
    },

    parseMapJSON: function (mapJSON) {
        gMap.currMapData = JSON.parse(mapJSON);

        var map = gMap.currMapData;

        gMap.numXTiles = map.width;
        gMap.numYTiles = map.height;

        gMap.tileSize.x = map.tilewidth;
        gMap.tileSize.y = map.tileheight;

        gMap.pixelSize.x = gMap.numXTiles * gMap.tileSize.x;
        gMap.pixelSize.y = gMap.numYTiles * gMap.tileSize.y;
        
        var img;

        for(var i = 0; i < map.tilesets.length; i++) {
            for (var gimme in map.tilesets[i]) {
                console.log('mmmh: ' + gimme);
            }
            img = new Image();
            img.onload = function () {
                gMap.imgLoadCount++;
                if (gMap.imgLoadCount === map.tilesets.length) {
                    gMap.fullyLoaded = true;
                }
            };

            img.src = map.tilesets[i].image;

            var ts = {
                "firstgid": map.tilesets[i].firstgid,

                "image": img,
                "imageheight": map.tilesets[i].imageheight,
                "imagewidth": map.tilesets[i].imagewidth,
                "name": map.tilesets[i].name,

                "numXTiles": Math.floor(map.tilesets[i].imagewidth / map.tilesets[i].tilewidth),
                "numYTiles": Math.floor(map.tilesets[i].imageheight / map.tilesets[i].tileheight)
            };

            this.tilesets.push(ts);
        }
    }
});

var gMap = new TILEDMapClass();